Eating or drinking by mistake does not break the fast, though it is better if the food or drink can be removed before it hits the person's throat. If someone deliberately breaks their fast, they must free one slave, fast for 60 more days, feed 60 needy persons or spend in charity an amount equal to feeding 60 persons. We call this kaffarah, which means "what is paid to redress an imbalance or to compensate for commissioning a sinful act".
Here are some other things that do not break the fast: unintentional vomiting; swallowing things that you can't avoid, such as one's own saliva, street dust, smoke, etc; brushing your teeth (thank goodness), although gargling is not recommended; unintentionally swallowing water while bathing; and IV injections that are solely medicinal and not nutritional.
